This study will investigate the effects of an EEG theta/beta ratio Neurofeedback training using a case series multiple baseline design. Twelve participants will be assigned to one of three different groups that have a different time of intervention onset, or include placebo sessions only. The investigators will examine whether the theta/beta ratio Neurofeedback training will reduce resting state theta/beta ratio. As a pilot-exploration for future studies, also performance on a cognitive interference task will be monitored to see if any improvement after NFT on cognitive performance might be a viable subject for future studies. All participants (healthy, but selected for above-median theta/beta ratio in previous studies in this lab) will start with three resting state EEG baseline sessions, the first participant group then continues with 14 theta/beta ratio Neurofeedback sessions, the second group continues with six extra baseline EEG measurements, followed by eight Neurofeedback training sessions while the third group will continue with 14 placebo training sessions only. EEG resting state theta/beta ratio and interference performance will be measured during every session.